Use -O1 for jemalloc unit tests

The current clang prebuilt hangs forever on test/unit/atomic.c when
compiling for aarch64, set the tests to -O1 until a prebuilt with the
fix is available.

Bug: 23256622
Change-Id: I12fe1ad28c278e364b966bf4904e26644e54cb95
1 file changed